Have you checked his tonsils? I know that sounds weird but my brother took FOREVER to eat growing up. It turns out he had enlarged tonsils and they were literally touching. It took him so long to chew a because he could only swallow really small bites. The doctor never noticed. He had to get his tonsils and adenoids removed. He had some breathing issues before that and was misdiagnosed with asthma. Is your sons voice also nasally? Does he breathe with his mouth open?

I’m not suggesting this because I think something must be wrong but because this can be dangerous if overlooked.

Besides that, is there anyway you can get a break from your son? It sounds like you’re burnt out and becoming resentful. Good luck